1. Field of the Invention
The present invention relates to a focusing technology of an electronic camera, and more particularly to a camera which can change a compressibility when an electronic image is stored, and switch a focusing method.
2. Description of the Related Art
Additionally, the present invention relates to an improvement of a so-called autofocus technology of a digital camera which electronically records an object image obtained through a taking lens by an imager.
In focusing of the electronic camera, a system called a climbing type imager AF (autofocus) which uses a photographing imager but no special sensors is often used.
In the imager AF, however, it is necessary to monitor a change made in contrast of the object on the imager in accordance with a focusing position of the taking lens, and a time lag during releasing often becomes a problem.
Thus, different focusing systems are disposed to correct the problem. For example, see Jpn. Pat, Appln. KOKAI Publication Nos. 2001-141985, 2001-249267, 2001-255456 etc.
On the other hand, various improvements have been made regarding image compression. The applicant of the present invention has filed Patent No. 3115912 etc. This regards a technology of changing a compressibility during image recording by using information obtained when the imager AF is operated. Similar technologies are disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2000-201287 etc.
An advantage of the imager AF is that even if there is an error in a stop position of the taking lens, a focusing position including the error is controlled, and thus feedback control which cancels the error can be carried out even in the case of lens position characteristics different from design due to a temperature, humidity or posture difference etc.
However, since it takes time until focusing as described above, in the cameras described in Jpn. Pat. Appln. KOKAI Publication Nos. 2001-141985 and 2001-249267, in a situation of a large focal depth, the previous lens position error is ignored, and focus control (LD) is carried out only based on a result of an external light AF.
In the distance measurement apparatus described in Jpn. Pat. Appln. KOKAI Publication No. 2001-255456, two systems are switched depending on a mode.
However, there may be a scene to be focused more accurately even if a focal depth is large, and a scent to be photographed by eliminating a release time lag even if a focal depth is small. Thus, setting by a mode is burdensome. Therefore, if priority can be switched between focusing and a time lag depending on a scene, it is possible to provide a camera more satisfactory to a user.